There has so far been known a torsion vibration damping apparatus which is adapted to connect a drive source such as an internal combustion engine and an electric motor with wheels to transmit the torque from the drive source to the wheels, and to absorb torsion vibration between the drive source and a drive transmission system having transmission gear assemblies.
As a conventional torsion vibration damping apparatus of this kind, there has so far been known an apparatus (for example see Patent Document 1) as shown in FIG. 12. In FIG. 12, the known torsion vibration damping apparatus 1 is provided with a hub member 4 having a hub flange 3 formed with a plurality of projections 2 radially extending and circumferentially spaced apart from one another through recesses 2a. The inner peripheral portion of the hub member 4 is splined to an input shaft forming part of a transmission included in a drive transmission system.
In the axial direction of the hub member 4 is provided a pair of disc plates 5, 6 which are in coaxial relationship with the hub member 4 to have the hub member 4 intervene between the disc plates 5, 6 in such a manner that the disc plates 5, 6 are relatively rotatable with the hub member 4 to which the torque is transmitted from the drive source such as the internal combustion engine.
The disc plates 5, 6 are respectively formed with accommodation holes 5a, 6a in opposing relationship with the recesses 2a. In the recesses 2a and the accommodation holes 5a, 6a are respectively arranged coil springs 7 in such a manner that the both circumferential end portions of the coil springs 7 are engaged with and compressed by the projection portions 2, so that the coil springs 7 are retained by the projection portions 2.
The torsion vibration damping apparatus 1 is operative to have the coil springs 7 resiliently deformed when the hub member 4 is twisted (relatively rotated) in the positive side, i.e., an acceleration side of the vehicle with respect to the disc plates 5, 6 and twisted in the negative side, i.e., a deceleration side of the vehicle with respect to the disc plates 5, 6, thereby damping the vibration between the internal combustion engine and the drive transmission system while the torque is being transmitted between the hub member 4 and the disc plates 5, 6.
The disc plates 5, 6 are provided with a plurality of stoppers 8 positioned on the paths of the projection portions 2 in such a manner that the stoppers 8 are engageable with the circumferential side surfaces of the projection portions 2 to regulate the relative rotations of the hub member 4 and the disc plates 5, 6.
Accordingly, the coil springs 7 can be prevented from excessively compressed and thus can prevent the coil springs 7 from being damaged and deteriorated in property.
On the other hand, it is well known that there are generated noises by the torsion vibration at the time of the vehicle cruising. The noises include cluttering sounds of gears generated by the torsion vibration stemmed from the rotation fluctuation caused by the torque fluctuation of the drive source during the times of the vehicle accelerated and decelerated, and by the collision of the idling gear pairs of the transmission gear assembly caused by the torsion resonance of the drive transmission system.
Further, there has occasionally been generated a large torsion vibration with a transitional torque inputted into the hub member when the hub member 4 is twisted in the positive side with respect to the disc plates 5, 6 in such a situation as causing the wheels to be fluctuated in speeds during the acceleration stage of the vehicle.
More concretely, as shown in FIG. 13, the torque is gradually raised as shown in a broken line when the vehicle is cruising on a flat road at the time of the acceleration stage, while the torque is fluctuated and raised as shown in a solid line when the vehicle is cruising on a bad road such as a rugged road and the like at the time of the acceleration stage.
This is due to the fact that the speed fluctuations of the wheels are generated when the vehicle is cruising on the bad road rather than the flat road. Therefore, when the condition under which the vehicle is cruising on the flat road is transferred to the condition under which the vehicle is cruising on the bad road, the large torque is transitionally inputted to the drive transmission system at the time of the vehicle being accelerated, thereby leading to generating a large torsion vibration.
For this reason, in order to damp the large torsion vibration caused by the transitional torque inputted to the drive transmission system at the time of the vehicle being accelerated, it is effective that the coil spring 7 is of low rigidity and has an enlarged torsion angle in its positive side. For making the coil spring 7 to be of low rigidity, the coil spring 7 is made large in its circumferential direction, thereby making it possible to easily operate the apparatus.